Wouldn’t it be nice if when your stuff broke, it could just fix itself, like how a living thing can heal a wound?
Self-healing materials have been a hot topic in science research for several years now. There are a few different ways people have tried to make this work, but a group of German scientists led by Professor Christopher Barner-Kowollik have come up with a system that is fast, heat activated and can heal and re-heal apparently indefinitely.
Healing as Good as New
In this new plastic, if there’s a crack or even a complete break, you just need to put the sides back together and heat it to 120°C, and it sticks back together within five minutes.
The scientists tested the strength of a disc of their plastic until it broke. They then reassembled it and heated it so it healed, and tested again. And again. They found that it healed to be just as strong as it was before.
New Technology from an Old Nobel
This new plastic is made of a mix of two components: a fairly normal acrylic plastic, and a linker chemical. The chemical structure of the acrylic plastic has been changed slightly from normal so that the linker chemical can connect to it.
To make the connection, the linker attaches to the acrylic plastic a little bit like a snap fastener closing. Heating it up gives this chemical snap fastener the energy it needs to come undone again. This snap-together chemical process is called the Diels-Alder reaction, named after the two German chemists who discovered it in 1928.
Otto Paul Hermann Diels and Kurt Alder were awarded the Nobel Prize for their reaction in 1950. The Diels-Alder reaction is important because it is one of very few reactions that can let two chemicals join and separate again unchanged, without necessarily needing to add anything else in.
It’s the fact that this reaction can let the chemicals snap together and come apart without changing them that lets the plastic heal itself so effectively over and over again.
A Promising System
The group’s work has been published in Advanced Materials, a scientific journal dedicated to innovative new materials of all types.
In their paper, they write that they believe the chemistry of this type of self-healing will be able to be used in many other types of plastics, making it “very useful for … rapid prototyping, adhesives, composite materials, coatings and paints as well as sealents (sic).”